The only leopard I have shot was with my .375 Holland & Holland magnum and a Hornady Interlock 300 gr. The leopard went down of his tree, stone dead, before hitting the ground. The exit wound was pretty big but it was the only rifle I had that was suitable for hunting this animal. The other was a long range rifle.
It means my experience is very limited but for hunting leopard, the caliber won't be my first concern because the animal is not so big. I think everything from .270 Winchester will do the job on leopard. I won't even be scaried to shoot a leopard even with my 6.5 Creedmoor, and a good Interlock 160 gr or a Nosler Partition 140 gr.
I would prefer to have first a high quality scope with a big objective to gather the biggest amount of light possible. For my eyes, German and Austrian scope with 50 or 56 mm objective are the best.
Such animal is usually shot in low light condition and I prefer to see them well through the scope to insure my shot and avoid problems later.
A friend shot many leopards with .30-06 and classic PMP Soft Point 180 gr and it always did the trick when the cat was well touched. But if you shoot in guts, I don't think a .375 H&H magnum will make a big difference ?
Better to shoot such potential dangerous animal with a rifle you trust.
